The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Viltrox AF 20mm f2.8 E and the Pentax 21mm F3.2 AL L for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Viltrox AF 20mm f2.8 E is the longer of the two lenses at 60mm. The Pentax 21mm F3.2 AL L with a length of 25mm, is 35mm shorter. Besides being longer, the Viltrox AF 20mm f2.8 E also has a larger diameter of 65mm compared to the Pentax 21mm F3.2 AL L's 63mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Pentax 21mm F3.2 AL L weighs 134g, 14% (23g) lighter than the Viltrox AF 20mm f2.8 E's weight of 157g.
Filter Threads
The Viltrox AF 20mm f2.8 E has a filter size of 52mm whereas the Pentax 21mm F3.2 AL L has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 52mm filters that we recommend you to consider for the Viltrox AF 20mm f2.8 E:
And these are the 49mm filters that we recommend for the Pentax 21mm F3.2 AL L:
Lens Mounts
The Viltrox AF 20mm f2.8 E has the Sony E lens mount whereas the Pentax 21mm F3.2 AL L has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Pentax 21mm F3.2 AL L is also available in Pentax KAF mount.
Focal Range
Viltrox AF 20mm f2.8 E is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30mm.
On the other hand, the Pentax 21mm F3.2 AL L is a prime lens with fixed focal lenght of 21mm which has an effective (full-frame 35mm equivalent) focal range of 31.5mm when used on a APS-C / DX format camera.
